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IMMUNITY

IMMUNITY. What is Immunity?. Ability of the body to protect itself from viruses, bacteria, and other disease causing agents The word immunity comes from the Latin word immunis meaning exempt. IMMUNE SYSTEM. SPECIFIC response to foreign substances

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IMMUNITY

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  1. IMMUNITY

  2. What is Immunity? • Ability of the body to protect itself from viruses, bacteria, and other disease causing agents • The word immunity comes from the Latin word immunis meaning exempt

  3. IMMUNE SYSTEM • SPECIFIC response to foreign substances • Substances that evoke the response are called ANTIGENS • Immune response produces proteins that are specific to the antigen, these are ANTIBODIES • Specific white blood cells called LYMPHOCYTES are produced

  4. Naturally acquired immunity Artificially acquired immunity Types of Acquired Immunity

  5. ACTIVE – exposure to antigen naturally in the course of daily life This is the type of immunity from having a disease PASSIVE – maternal antibodies transferred via the placenta or mother’s milk Temporary immunity for the newborn Naturally acquired immunity

  6. ACTIVE – vaccination Receive antigen via injection of vaccine Produce antibodies against the injected antigen PASSIVE – preformed antibodies Receive preformed antibodies from immune person or animal Antiserum Temporary protection Artificially acquired immunity

  7. Humoral immunity Production of antibodies B cell activation Active against bacteria, toxins, and viruses that are circulating in body fluids Cell-mediated immunity Activation of T cells Active bacteria and viruses that are inside host cells Duality of Immune System

  8. What are Antigens? • Things that are foreign to our body • Usually proteins or large polysaccharides • Antigenic determinants are often parts of the invading microbe • Antibodies react with specific regions of the antigen called EPITOPES

  9. Antigenic determinants

  10. What are Antibodies? • Antibodies are proteins • React with only ONE specific antigen • Neutralize or destroy the antigen • Each antibody has specific antigen binding sites

  11. Antibody structure • Consists of 4 chains • 2 light and 2 heavy chains • Variable regions of antibody bind specific antigen

  12. Antibody structure

  13. Antibody variable regions(antigen binding sites)

  14. Classes of Antibodies(Immunoglobulins) • IgG • IgM • IgA • IgD • IgE

  15. IgG • Single unit monomer antibody • 80% of all antibodies are of this class • Crosses the placental barrier to protect fetus • Protects against CIRCULATING bacteria, viruses, and toxins

  16. IgM • 5 monomer antibody • 5-10% of antibody in serum • First class of antibodies formed to antigen • Reacts with human ABO blood groups • Clumps the antigen

  17. IgA • 2 unit monomer antibody • 10-15% of antibodies in serum • Abundant in mucous membranes, tears, saliva, and breast milk • Prevents pathogen attachment to mucosal surfaces

  18. IgD • Single unit monomer antibody • 0.2% of serum antibody • Found in blood and lymph • Antigen receptor on B cells

  19. IgE • Single unit monomer antibody • 0.002% of antibodies in serum • Binds to mast cells and basophils • Allergic reactions

  20. B cells • Develop in the bone marrow • Migrate to lymph nodes and spleen • Recognize antigen by cell surface receptors • Activated B cells divide to form plasma cells which secrete antibody

  21. Clonal Selection • B cell is sensitized by specific antigen • Divides to form many more identical cells (clones) • The clones differentiate into plasma cells that secrete antibody formed against the antigen • Some cells become memory cells to provide protection for years to come

  22. Clonal Selection

  23. Results of Antigen-Antibody Binding • 1. Agglutination • 2. Opsonization • 3. Neutralization • 4. Complement activation • 5. Inflammation

  24. Results of Antigen-Antibody Binding

  25. Monoclonal Antibody Production

  26. Uses of Monoclonal Antibodies • Diagnostic kits • Pregnancy testing • Suppression of tissue rejection in transplants • Disease treatment

  27. Primary and Secondary Immune Response • Primary response to antigen is by IgM antibodies • IgG antibody production begins several days later • Second exposure to antigen results in IgG production immediately and in large quantities • Anamnestic (memory) response

  28. Memory response

  29. Cell-mediated Immunity • Based on the activity of T cells • T cells are a class of lymphocytes that are produced in the bone marrow but mature in the thymus gland • Distributed in the various lymphatic organs • Effective against intracellular antigens

  30. What are Cytokines and Interleukins? • Cytokines are the chemical messengers of the immune system • Interleukins are the cytokines that serve as communicators between white blood cells • There are now at least 26 different interleukins (IL) many of which have important functions in the immune system

  31. T cells • T cells are the key cellular component of immunity • There are 4 main types of T cells • T Helper cells* • Cytotoxic T cells* • Delayed hypersensitivity T cells • Suppressor T cells

  32. CD – no not compact discs(Cluster of differentiation) • T cells carry surface receptors called CD’s that are used to differentiate between the various types of T cells • T helper cells are classified as CD4 cells by their receptor • Cytotoxic T cells are CD8 cells

  33. T Helper cells • Key cell that activates cell-mediated immunity and links humoral (antibody) immunity to cell-mediated immunity • The T helper cell is attacked and destroyed by the AIDS virus leading to immune system failure

  34. T - helper cells and HIV Time course

  35. Helper cell activation • Antigen is presented to the helper cell by another cell called an APC cell • APC cell and T helper cell bind • APC cell secretes IL-1, T helper cell is now activated! • IL-1 simulates the T helper cell to secrete IL-2 • IL-2 secretion stimulates the activated T(H) cell to form clones of itself and also to stimulate other cells such as B cells to make antibody, and T(C) to attack infected cells

  36. T helper cell activation

  37. Cytotoxic T cells • Once activated by the T(H) cell the T(C) seek out and destroy infected cells in the body • The T(C) bind with infected cells and release PERFORIN that causes the infected cells to burst (lyse)

  38. Cytotoxic T cell activity

  39. How the Cytotoxic T cells works

  40. T cell/B cell interaction

  41. T cell/B cell interaction

  42. Immune system summary

  43. Summary of cell-mediated immunity • APC’s stimulate the T(H) cell • The T(H) cell is central to both humoral and cell-mediated immunity • T(H) cells stimulate B cells to make antibody and cytotoxic T cells to destroy infected cells • Without T(H) both aspects of immunity will fail and so will you!

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